All-digital phase locked loop using switched capacitor voltage doubler

ABSTRACT

An all-digital phase locked loop (ADPLL) receives an analog input supply voltage which is utilized to operate analog circuitry within the ADPLL. The ADPLL of the present disclosure scales this analog input supply voltage to provide a digital input supply voltage which is utilized to operate digital circuitry within the ADPLL. The analog circuitry includes a time-to-digital converter (TDC) to measure phase errors within the ADPLL. The TDC can be characterized as having a resolution of the TDC which is dependent, at least in part, upon the digital input supply voltage. In some situations, process, voltage, and/or temperature (PVT) variations within the ADPLL can cause the digital input supply voltage to fluctuate, which in turn, can cause fluctuations in the resolution of the TDC. These fluctuations in the resolution of the TDC can cause in-band phase noise of the ADPLL to vary across the PVT variations. The digital circuitry regulates the digital input supply voltage to stabilize the resolution of the TDC across the PVT variations. This stabilization of the resolution of the TDC can cause the ADPLL to maintain a fixed in-band phase noise across the PVT variations.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. Provisional Patent Appl. No. 62/514,402, filed Jun. 2, 2017, which is incorporated herein by reference in its entirety.

BACKGROUND

The Internet of Things (IoT) represents an ever-growing inter-network of physical devices, vehicles, buildings, and/or things that are embedded with electronics, software, sensors, actuators, and network connectivity which enable these devices, vehicles, buildings, and/or things to exchange data. These physical devices, vehicles, buildings, and/or things collect information and then autonomously communicate this information to other physical devices, vehicles, buildings, and/or things. As such, these physical devices, vehicles, buildings, and/or things include transmitters for transmitting this information to the other physical devices, vehicles, buildings, and/or things and receivers for receiving other information from the other physical devices, vehicles, buildings, and/or things. For example, lighting systems, heating systems, ventilation systems, air conditioning systems, and/or household appliances can include transmitters for communicating information relating to their status to mobile communication devices, such as mobile telephony devices, for example, mobile phones, mobile computing devices, mobile internet devices, for example, tablet computers and/or laptop computers. These lighting systems, heating systems, ventilation systems, air conditioning systems, and/or household appliances can include receivers for receiving information relating to their control from the mobile communication devices. At the heart of these transmitters and receivers lies a phase locked loop (PLL) for providing the signals necessary for transmitting this information to the other physical devices, vehicles, buildings, and/or things and for receiving the other information from the other physical devices, vehicles, buildings, and/or things.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 illustrates a block diagram of an all-digital phase locked loop (ADPLL) according to an exemplary embodiment of the present disclosure;

FIG. 2 further illustrates the block diagram of the ADPLL according to an exemplary embodiment of the present disclosure;

FIG. 3 illustrates a block diagram of first exemplary voltage doubler circuitry that can be implemented within the ADPLL according to an exemplary embodiment of the present disclosure;

FIG. 4 illustrates a block diagram of second exemplary voltage doubler circuitry that can be implemented within the ADPLL according to an exemplary embodiment of the present disclosure; and

FIG. 5 illustrates a flowchart of an exemplary operation of the ADPLL according to an exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Overview

An all-digital phase locked loop (ADPLL) receives an analog input supply voltage which is utilized to operate analog circuitry within the ADPLL. The ADPLL of the present disclosure scales this analog input supply voltage to provide a digital input supply voltage which is utilized to operate digital circuitry within the ADPLL. The analog circuitry includes a time-to-digital converter (TDC) to measure phase errors within the ADPLL. The TDC can be characterized as having a resolution of the TDC which is dependent, at least in part, upon the digital input supply voltage. In some situations, process, voltage, and/or temperature (PVT) variations within the ADPLL can cause the digital input supply voltage to fluctuate, which in turn, can cause fluctuations in the resolution of the TDC. These fluctuations in the resolution of the TDC can cause in-band phase noise of the ADPLL to vary across the PVT variations. The digital circuitry regulates the digital input supply voltage to stabilize the resolution of the TDC across the PVT variations. This stabilization of the resolution of the TDC can cause the ADPLL to maintain a fixed in-band phase noise across the PVT variations.

Exemplary all-Digital Phase Locked Loop (ADPLL)

FIG. 1 illustrates a block diagram of an all-digital phase locked loop (ADPLL) according to an exemplary embodiment of the present disclosure. An all-digital phase lock loop (ADPLL) 100 represents a closed-loop feedback control system for providing an output signal 152 which is proportional to a reference input signal 150. Although the present disclosure is to be described in terms of an ADPLL, those skilled in the relevant art(s) will recognize the teachings herein are applicable to other types of PLLs, such as an analog or linear PLL (APLL) or a digital PLL (DPLL) to provide some examples, without departing from the spirit and scope of the present disclosure. As illustrated in FIG. 1, the ADPLL 100 utilizes a combination of analog circuitry 102 and digital circuitry 104 to cause a frequency f_(OUT) and/or a phase ϕ_(OUT) of the output signal 152 to be proportional to a frequency f_(REF) and/or a phase ϕ_(REF) of the reference input signal 150.

Generally, the analog circuitry 102 operates on time-varying signals within the ADPLL 100. The analog circuitry 102 can include one or more resistors, one or more capacitors, one or more inductors, one or more diodes, and/or one or more transistors to provide some examples. In the exemplary embodiment illustrated in FIG. 1, the analog circuitry 102 includes the digital oscillator 108 to provide the output signal 152 which is proportional the reference input signal 150 and other analog circuitry 110. The other analog circuitry 110 can include one or more analog circuits, such as an analog buffer amplifier to provide an example, to assist the digital oscillator 108 to provide the output signal 152. In the exemplary embodiment illustrated in FIG. 1, the analog circuitry 102 receives the analog input supply voltage 154 which is needed to operate on the time-varying signals within the ADPLL 100.

The digital circuitry 104 operates on discrete signals representing logical and/or numeric values within the ADPLL 100. The digital circuitry 104 can include one or more logic gates to provide one or more Boolean logic functions, such as AND, OR, XOR, XNOR, and/or NOT to provide some examples, or a storage function, such as a flip-flop or a latch to provide some examples. In the exemplary embodiment illustrated in FIG. 1, the digital circuitry 104 includes a time-to-digital converter (TDC) 112 to measure a phase error between the reference signal 150 and the output signal 152 and other digital circuitry 114. The other digital circuitry 114 can include one or more digital circuits, such as digital combination circuitry, digital filtering circuitry, and/or digital dividing circuitry to provide some examples, to assist the TDC 112 to measure the difference between the reference signal 150 and the output signal 152. In the exemplary embodiment illustrated in FIG. 1, the digital circuitry 104 receives the digital input supply voltage 156 which is needed to operate on the discrete signals within the ADPLL 100.

Moreover, the ADPLL 100 additionally includes voltage doubler circuitry 106 to scale an analog input supply voltage 154 by a numerical factor, such as approximately two to provide an example, to provide a digital input supply voltage 156. In an exemplary embodiment, the voltage doubler circuitry 106 scales the analog input supply voltage 154 of approximately 0.5 V_(DC) to provide the digital input supply voltage 156 at approximately 1.0 V_(DC). In this exemplary embodiment, a resolution of the TDC 112 is dependent, at least in part, upon the digital input supply voltage 156. In some situations, process, voltage, and/or temperature (PVT) variations within the ADPLL 100 can cause the digital input supply voltage 156 to fluctuate, which in turn, can cause fluctuations in the resolution of the TDC 112. These fluctuations in the resolution of the TDC 112 can cause in-band phase noise of the ADPLL 100 to vary across the PVT variations. The other digital circuitry 114, as described above, can include one or more digital circuits to regulate the digital input supply voltage 156 to stabilize the resolution of the TDC 112 across the PVT variations. This stabilization of the resolution of the TDC 112 can cause the ADPLL 100 to maintain a fixed in-band phase noise across the PVT variations.

FIG. 2 further illustrates the block diagram of the ADPLL according to an exemplary embodiment of the present disclosure. An ADPLL 200 represents a closed-loop feedback control system for providing the output signal 152 which is proportional to the reference input signal 150. As illustrated in FIG. 2, the ADPLL 200 utilizes a combination of the analog circuitry 102 and the digital circuitry 104, as discussed above in FIG. 1, to cause the frequency f_(OUT) and/or the phase ϕ_(OUT) of the output signal 152 to be proportional to the frequency f_(REF) and/or the phase ϕ_(REF) of the reference input signal 150. In the exemplary embodiment illustrated in FIG. 2, the ADPLL 200 includes the analog circuitry 102, the digital circuitry 104, and the voltage doubler circuitry 106. The ADPLL 200 can represent an exemplary embodiment of the ADPLL 100 as discussed above in FIG. 1. It should be noted that various connections, which are not relevant to the discussion to follow, between the analog input supply voltage 154 and the analog circuitry 102 and between the digital input supply voltage 156 and the digital circuitry 104 as illustrated in FIG. 1 are not illustrated in FIG. 2 for convenience.

The analog circuitry 102 operates on time-varying signals within the ADPLL 200. In the exemplary embodiment illustrated in FIG. 2, the analog circuitry 102 includes the digital oscillator 108 and the other analog circuitry 110. The digital oscillator 108 adjusts a frequency f_(OUT) and/or a phase ϕ_(OUT) of an output signal 250 in accordance with a fine digital tuning signal 252 and a coarse digital tuning signal 254. The coarse digital tuning signal 254 coarsely tunes the frequency f_(OUT) to be within a locking range of the ADPLL 200. The locking range of the ADPLL 200 represents a range for the frequency f_(OUT) of the output signal 250 that is sufficiently close to the frequency f_(REF) of the reference input signal 150 such that the ADPLL 200 can lock onto the reference input signal 150 using the fine digital tuning signal 252. The fine digital tuning signal 252 can be used by the digital oscillator 108 to adjust the frequency f_(OUT) and the phase ϕ_(OUT) to match variations in the frequency f_(REF) and the phase ϕ_(REF) of the reference input signal 150. In an exemplary embodiment, the digital oscillator 108 is implemented using a digitally controlled oscillator (DCO); however, those skilled in the relevant art(s) will recognize that other implementation for the digital oscillator 108, such as a numerically controlled oscillator (NCO) or a direct digital synthesizer (DDS) to provide some examples, are possible without departing from the spirit and scope of the present disclosure. In another exemplary embodiment, the digital oscillator 108 can be implemented using the digital controlled oscillator as discussed in Kuo et. al, “A Fully Integrated 28 nm Bluetooth Low-Energy Transmitter with 36% System Efficiency at 3 dBm,” European Solid-State Circuits Conference (ESSCIRC), ESSCIRC 2015-41st (2015), which is incorporated herein by reference in its entirety.

As illustrated in FIG. 2, the other analog circuitry 110 includes an analog amplifier 204. The analog amplifier 204 amplifies the output signal 250 having the frequency f_(OUT) and the phase ϕ_(OUT) to provide the output signal 152 having the frequency f_(OUT) and the phase ϕ_(OUT). In an exemplary embodiment, the analog amplifier 204 is implemented using a buffer amplifier, such as a voltage buffer amplifier or a current buffer amplifier to provide some examples.

The digital circuitry 104 operates on discrete signals representing logical and/or numeric values within the ADPLL 200. In the exemplary embodiment illustrated in FIG. 2, the digital circuitry 104 includes the TDC 112 and the other digital circuitry 114 as described above in FIG. 1. In this exemplary embodiment, the other digital circuitry 114 includes a digital loop filter 206, a digital dividing circuitry 208, and calibration circuitry 210. The TDC 112 measures various timing characteristics between the reference input signal 150 and a clocking signal 258 to provide a digital phase error 256 representing a difference between the phase ϕ_(REF) of the reference input signal 150 and the phase ϕ_(OUT) of the clocking signal 258. For example, the TDC 112 measures a first start time of the reference input signal 150 and/or a first stop time of the reference input signal 150. In this example, the TDC 112 similarly measures a second start time of the clocking signal 258 and/or a second stop time of the clocking signal 258. Also in this example, the TDC 112 compares the first start time and the second start time and/or the first stop time and the second stop time to measure the difference between the phase ϕ_(REF) of the reference input signal 150 and the phase ϕ_(OUT) of the clocking signal 258 and provides a digital representation of this difference as the digital phase error 256. In the exemplary embodiment illustrated in FIG. 2, the TDC 112 receives operational power from the digital input supply voltage 156. As described above in FIG. 1, the PVT variations within the ADPLL 100 can cause the digital input supply voltage 156 to fluctuate, which in turn, can cause fluctuations in the resolution of the TDC 112. These fluctuations in the resolution of the TDC 112 can cause in-band phase noise of the ADPLL 100 to vary across the PVT variations. As to be described in further detail below, the other digital circuitry 114 includes calibration circuitry 210 to regulate the digital input supply voltage 156 to stabilize the resolution of the TDC 112 across the PVT variations. This stabilization of the resolution of the TDC 112 can cause the ADPLL 100 to maintain a fixed in-band phase noise across the PVT variations.

As additionally illustrated in FIG. 2, the other digital circuitry 114 includes a digital loop filter 206, digital dividing circuitry 208, and the calibration circuitry 210. The digital loop filter 206 provides the fine digital tuning signal 252 in response to the digital phase error 256. In an exemplary embodiment, the digital loop filter 206 is implemented using a digital low pass filter, such as a finite impulse response (FIR) low pass filter or an infinite impulse response (IIR) low pass filter to provide some examples. In this exemplary embodiment, the digital loop filter 206 suppresses high frequency components in the digital phase error 256 which are outside of its bandwidth to provide samples of a direct current (DC), or near DC, component of the digital phase error 256 within its bandwidth as the fine digital tuning signal 252.

The digital dividing circuitry 208 digitally divides the output signal 250 having the frequency f_(OUT) and the phase ϕ_(OUT) to provide the clocking signal 258 having the frequency f_(DIV) and the phase ϕ_(OUT). In the exemplary embodiment illustrated in FIG. 2, the digital dividing circuitry 208 is implemented as an integer frequency divider to digitally divide the frequency f_(OUT) of the output signal by an integer N, such as two to provide an example, to provide the clocking signal 258 having the frequency f_(DIV) and the phase ϕ_(DIV). However, those skilled in the relevant art(s) will recognize the digital dividing circuitry 208 can be implemented as a fractional frequency divider to digitally divides the frequency f_(OUT) of the output signal by a non-integer F, such as two and two-thirds to provide an example, to provide the clocking signal 258 having the frequency f_(DIV) and the phase ϕ_(DIV).

The calibration circuitry 210 regulates the digital input supply voltage 156 to stabilize the resolution of the TDC 112 across the PVT variations. In the exemplary embodiment illustrated in FIG. 2, the calibration circuitry 210 utilizes the digital phase error 256 to estimate the resolution of the TDC 112. In an exemplary embodiment, the resolution of the TDC 112 can be estimated using any well-known estimation mechanism that will be apparent to those skilled in the relevant art(s) without departing from the spirit and scope of the present disclosure. This well-known estimation mechanism can include the mechanism as described in U.S. patent application Ser. No. 12/134,081, filed Jun. 5, 2008, now U.S. Pat. No. 8,830,001, which is incorporated herein by reference in its entirety. Thereafter, the calibration circuitry 210 compares the estimated resolution of the TDC 112 to a target resolution for the TDC 112 and assigns a value to a voltage control signal 260 in response to this comparison. In an exemplary embodiment, the voltage control signal 260 causes the voltage doubler circuitry 106, having one or more switched capacitor circuits, to generate a switching clocking signal to charge and/or to discharge the one or more switched capacitor circuits to provide the digital input supply voltage 156 when the estimated resolution of the TDC 112 is less than the target resolution for the TDC 112. Otherwise, the voltage control signal 260 causes the voltage doubler circuitry 106 to skip one or more clocking cycles of the switching clocking signal to decrease the digital input supply voltage 156 when the estimated resolution of the TDC 112 is greater than or equal to the target resolution for the TDC 112. In this situation, the estimated resolution of the TDC 112 can be considered to be too fine when compared to the target resolution for the TDC 112.

In the exemplary embodiment illustrated in FIG. 3, the calibration circuitry 210 assigns the value to the voltage control signal 260 in accordance with a calibration table. An exemplary embodiment for the calibration table is shown below in TABLE 1.

TABLE 1 Exemplary Calibration Table resolution of the TDC voltage control signal 260 112 11 . . . 11 0.01 Unit Interval (UI) 11 . . . 10 0.011 UI  . . . . . . 10 . . . 00 0.25 UI . . . . . . 00 . . . 01 0.49 UI 00 . . . 00 >_0.5 UI  

TABLE 1 illustrates the progression of the voltage control signal 260 from its maximum value of 11 . . . 11 to its minimum value 00 . . . 00 and corresponding values for the resolution for the TDC 112 between the maximum value and the minimum value. As illustrated by TABLE 1, the calibration circuitry 210 assigns the voltage control signal 260 to a value between 11 . . . 11 and 00 . . . 01 when a ratio between the estimated resolution of the TDC 112 and the target resolution for the TDC 112, expressed in unit intervals (UI), is between 0.01 UI and 0.49 UI. In this situation, the voltage control signal 260 causes the voltage doubler circuitry 106, having one or more switched capacitor circuits, to generate a switching clocking signal to charge and/or to discharge the one or more switched capacitor circuits to provide the digital input supply voltage 156. Otherwise, the calibration circuitry 210 assigns the voltage control signal 260 to a value of 00 . . . 00 when the ratio between the estimated resolution of the TDC 112 and the target resolution for the TDC 112 is greater than or equal to 0.50 UI. In this situation, the voltage control signal 260 causes the voltage doubler circuitry 106 to skip one or more clocking cycles of the switching clocking signal to decrease the digital input supply voltage 156.

As discussed above in FIG. 1, the voltage doubler circuitry 106 scales the analog input supply voltage 154 by the numerical factor, for example approximately two, to provide the digital input supply voltage 156. In the exemplary embodiment illustrated in FIG. 2, the voltage doubler circuitry 106 provides the switching clocking signal to activate, namely charge, and/or deactivate, namely discharge, the one or more switched capacitor circuits to provide the digital input supply voltage 156. The one or more switched capacitor circuits store energy from analog input supply voltage 154 when activated and discharge this stored energy when deactivated to provide the digital input supply voltage 156. In some situations, for example, when the voltage control signal 260 is at the value of 00 . . . 00, the voltage doubler circuitry 106 can skip one or more clocking cycles of the switching clocking signal to decrease the digital input supply voltage 156 to stabilize the resolution of the TDC 112 across the PVT variations.

Exemplary Voltage Doubler Circuitry

FIG. 3 illustrates a block diagram of first exemplary voltage doubler circuitry that can be implemented within the ADPLL according to an exemplary embodiment of the present disclosure. As illustrated in FIG. 3, voltage doubler circuitry 300 scales the analog input supply voltage 154 by the numerical factor to provide the digital input supply voltage 156. The voltage doubler circuitry 300 can include control logic circuitry 302, oscillator circuitry 304, and a switchable capacitor circuitry 306. The voltage doubler circuitry 300 can represent an exemplary embodiment of the voltage doubler circuitry 106.

The control logic circuitry 302 decodes the voltage control signal 260 to provide an oscillator circuitry control signal 350. In the exemplary embodiment illustrated in FIG. 3, the control logic circuitry 302 includes one or more logical gates, such as one or more logical AND gates, one or more logical OR gates, one or more logical INVERTER gates, one or more logical NAND gates, one or more logical NOR gates, or any combination thereof to provide some examples, to decode the voltage control signal 260 to provide the oscillator circuitry control signal 350. For example, from TABLE 1 above, the one or more logical gates provide the oscillator circuitry control signal 350 at a first logical level, such as a logical zero to provide an example, when the voltage control signal 260 is at 00 . . . 00. Otherwise in this example, the one or more logical gates provide the oscillator circuitry control signal 350 at a second logical level, such as a logical one to provide an example, when the voltage control signal 260 is between 11 . . . 11 and 00 . . . 01.

The oscillator circuitry 304 provides the switching clocking signal 352 when the oscillator circuitry control signal is at the first logical level or skips one or more clocking cycles of the switching clocking signal 352 when the oscillator circuitry control signal 350 is at the second logical level. In an exemplary embodiment, the oscillator circuitry 304 can include a feedback oscillator, such as an RC oscillator circuit, an LC oscillator circuit, or a crystal oscillator circuit; a negative resistance oscillator, such as a Clapp oscillator, a Colpitts oscillator, a Hartley oscillator, a Pierce oscillator, or a Wien bridge oscillator; or a relaxation oscillator, such as a multivibrator, a ring oscillator, or a delay line oscillator to provide some examples. The operation of the oscillator circuitry 304 is to be described using an enhanced view of the switching clocking signal 352 as illustrated in FIG. 3. As illustrated in the enhanced view of the switching clocking signal 352, the switching clocking signal 352 switches between a first logical level 354, such as a logical zero to provide an example, and a second logical level 356, such as a logical one to provide an example, when the oscillator circuitry 304 is at the first logical level. Otherwise, the switching clocking signal 352 skips one or more clocking skipped cycles 358 when the oscillator circuitry 304 is at the second logical level. As additionally illustrated in the enhanced view of the switching clocking signal 352, the switching clocking signal 352 is at the first logical level 354 during the one or more clocking skipped cycles 358.

The switchable capacitor circuitry 306 scales the analog input supply voltage 154 in accordance with the switching clocking signal 352 to provide the digital input supply voltage 156. In the exemplary embodiment illustrated in FIG. 3, the switchable capacitor circuitry 306 includes one or more switchable capacitors to provide the digital input supply voltage 156. The switching clocking signal 352 activates, namely charges, the one or more switchable capacitors when at the second logical level 356 and/or deactivates, namely discharges, the one or more switchable capacitors when at the first logical level 354 to provide the digital input supply voltage 156. The one or more switchable capacitors store energy when activated from analog input supply voltage 154 and discharge this stored energy when deactivated to provide the digital input supply voltage 156 at its current voltage level. In some situations, the switching clocking signal 352 deactivates, namely discharges, the one or more switchable capacitors when the one or more clocking skipped cycles 358 to decrease the digital input supply voltage 156 over a duration of the one or more clocking skipped cycles 358.

FIG. 4 illustrates a block diagram of second exemplary voltage doubler circuitry that can be implemented within the ADPLL according to an exemplary embodiment of the present disclosure. Voltage doubler circuitry 400 scales the analog input supply voltage 154 by the numerical factor to provide the digital input supply voltage 156. The voltage doubler circuitry 400 can include the control logic circuitry 302, multi-phase oscillator circuitry 402, and switchable capacitor circuitry 404.1 through 404.k. The voltage doubler circuitry 400 can represent an exemplary embodiment of the voltage doubler circuitry 106.

The multi-phase oscillator circuitry 402 provides multiple phases 452.1 through 452.k of a switching clocking signal, such as the switching clocking signal 352 to provide an example, when the oscillator circuitry control signal 350 is at the first logical level or skips the one or more clocking cycles of the multiple phases 452.1 through 452.k of the switching clocking signal when the oscillator circuitry control signal 350 is at the second logical level. In the exemplary embodiment illustrated in FIG. 4, the multiple phases 452.1 through 452.k of the switching clocking signal are offset by approximately

. In an exemplary embodiment, the multiple phases 452.1 through 452.k of the switching clocking signal include the multiple phases 452.1 and 452.2 of the switching clocking signal. In this exemplary embodiment, the multiple phases 452.1 and 452.2 of the switching clocking signal are offset by approximately

. Also, in the exemplary embodiment illustrated in FIG. 4, the multiple phases 452.1 through 452.k of the switching clocking signal represents differential multiple phases 452.1 through 452.k of the switching clocking signal. In this exemplary embodiment, the multiple phases 452.1 through 452.k of the switching clocking signal include the multiple phases 452.1 ₍₊₎ through 452.k ₍₊₎ of the switching clocking signal and with their complementary multiple phases 452.1 ⁽⁻⁾ through 452.k ⁽⁻⁾ of the switching clocking signal which are offset from the multiple phases 452.1 ₍₊₎ through 452.k ₍₊₎ of the switching clocking signal by approximately π.

The switchable capacitor circuitry 404.1 through 404.k scales the analog input supply voltage 154 in accordance with the multiple phases 452.1 through 452.k of the switching clocking signal to provide the digital input supply voltage 156. In the exemplary embodiment illustrated in FIG. 3, each of the switchable capacitor circuitry 404.1 through 404.k includes one or more switchable capacitors to provide the digital input supply voltage 156. The multiple phases 452.1 through 452.k of the switching clocking signal activates, namely charges, the one or more switchable capacitors of their corresponding switchable capacitor circuitry 404.1 through 404.k when at the second logical level, such as a logical one, and/or deactivates, namely discharges, the one or more switchable capacitors of their corresponding switchable capacitor circuitry 404.1 through 404.k when at a first logical level, such as a logical zero, to contribute to the digital input supply voltage 156. In some situations, the multiple phases 452.1 through 452.k of the switching clocking signal deactivate, namely discharge, their corresponding switchable capacitor circuitry 404.1 through 404.k when one or more clocking cycles of the multiple phases 452.1 through 452.k of the switching clocking signal have been skipped in response to the multi-phase oscillator circuitry 402 being disabled. In these situations, this discharge of the one or more switchable capacitors of the switchable capacitor circuitry 404.1 through 404.k decreases the digital input supply voltage 156.

Exemplary Operation of the Electronic Optimization Platform

FIG. 5 illustrates a flowchart of an exemplary operation of the ADPLL to compensate for process, voltage, and temperature (PVT) variations within the ADPLL according to an exemplary embodiment of the present disclosure. The disclosure is not limited to this operational description. Rather, it will be apparent to ordinary persons skilled in the relevant art(s) that other operational control flows are within the scope and spirit of the present disclosure. The following discussion describes exemplary operation flow 500 for a ADPLL, such as the ADPLL 100 and/or the ADPLL 200 to provide some examples, to compensate for process, voltage, and temperature (PVT) variations.

At operation 502, the exemplary operation flow 500 estimates a resolution of a time-to-digital converter (TDC) of the ADPLL. In an exemplary embodiment, the exemplary operation flow 500 can estimate the resolution of the TDC can be estimated using any well-known estimation mechanism that will be apparent to those skilled in the relevant art(s) without departing from the spirit and scope of the present disclosure. This well-known estimation mechanism can include the mechanism as described in U.S. patent application Ser. No. 12/134,081, filed Jun. 5, 2008, now U.S. Pat. No. 8,830,001, which is incorporated herein by reference in its entirety.

At operation 504, the exemplary operation flow 500 determines whether the resolution of the TDC estimated in operation 502 is greater than or equal to a target resolution for the TDC. The exemplary operation flow 500 proceeds to operation 506 when the TDC estimated in operation 502 is less than the target resolution for the TDC. Otherwise, the exemplary operation flow 500 proceeds to operation 508 when the TDC estimated in operation 502 is greater than or equal the target resolution for the TDC.

At operation 506, the exemplary operation flow 500 provides a switching clocking signal, such as the switching clocking signal 352 or the multiple phases 452.1 through 452.k of the switching clocking signal to provide some examples, that switches between a first logical level, such as a logical zero, and a second logical level, such as a logical one.

At operation 508, the exemplary operation flow 500 skips one or more clocking cycles of the switching clocking signal when the TDC estimated in operation 502 is greater than or equal the target resolution for the TDC.

At operation 510, the exemplary operation flow 500 charges and/or discharges one or more switched capacitor circuits, such as the switchable capacitor circuitry 306 or the switchable capacitor circuitry 404.1 through 404.k to provide some examples, in accordance with the switching clocking signal. The exemplary operation flow 500 discharges the one or more switched capacitor circuits when the switching clocking signal is at the first logical level, such as the logical zero, to increase a first analog supply voltage, such as the digital input supply voltage 156 to provide an example, and charges the one or more switched capacitor circuits when the switching clocking signal is at the second logical level, such as the logical one, using a second analog supply voltage, such as the analog input supply voltage 154 to provide an example. In an exemplary embodiment, the exemplary operation flow 500 discharges the one or more switched capacitor circuits when the switching clocking signal is at the first logical level for the duration of the duration of the one or more clocking cycles from operation 506 that have been skipped to regulate a digital input supply voltage to stabilize the resolution of the TDC across the PVT variations.

CONCLUSION

The foregoing Detailed Description discloses a phase locked loop (PLL). The PLL includes a time-to-digital converter (TDC), calibration circuitry, and a digital oscillator. The TDC measures a phase error difference between a phase of a first signal and a phase of a second signal. The calibration circuitry estimate a resolution of the TDC and compares the estimated resolution of the TDC to a target resolution. The voltage doubler circuitry charges or discharges one or more switchable capacitors in accordance with a switching clocking signal to provide a supply voltage when the estimated resolution of the TDC is less than to the target resolution, and skips one or more cycles of the switching clocking signal to decrease the supply voltage when the estimated resolution of the TDC is greater than or equal to the target resolution. The TDC receives operational power from the supply voltage. The digital oscillator provides the second signal in response to the phase error difference.

The foregoing Detailed Description also discloses a method for compensating for process, voltage, and temperature (PVT) variations within a phase locked loop (PLL). The method includes measuring a phase error difference between a phase of a first signal and a phase of a second signal, estimating a resolution of a time-to-digital converter (TDC) with the PLL based upon the phase error difference, generating a switching clocking signal when the estimated resolution of the TDC is less than to a target resolution, the switching clocking signal switching between a first logical level and a second logical level, skipping one or more clocking cycles of the switching clocking signal when the estimated resolution of the TDC is greater than or equal to a target resolution, the switching clocking signal being at the first logical level for a duration of the one or more clocking cycles of the switching clocking signal, discharging one or more switched capacitor circuits when the switching clocking signal is at the first logical level; and charging the one or more switched capacitor circuits when the switching clocking signal is at the second logical level.

The foregoing Detailed Description further discloses a system for compensating for process, voltage, and temperature (PVT) variations within a phase locked loop (PLL). The system includes a time-to-digital converter (TDC), an oscillator, and one or more switchable capacitors. The TDC measures a phase error difference between a phase of a first signal and a phase of a second signal. The oscillator is enabled to generate a switching clocking signal when a resolution of the TDC is less than a target resolution for the TDC, the switching clocking signal switching between a first logical level and a second logical level and disabled to skip one or more clocking cycles of the switching clocking signal when the resolution of the TDC is greater than or equal to the target resolution for the TDC, the switching clocking signal being at the first logical level for a duration of the one or more clocking cycles of the switching clocking signal. The one or more switchable capacitors are discharged when the switching clocking signal is at the first logical level and to be charged when the switching clocking signal is at the second logical level to provide a supply voltage. The TDC receives operational power from the supply voltage.

The foregoing Detailed Description referred to accompanying figures to illustrate exemplary embodiments consistent with the disclosure. References in the foregoing Detailed Description to “an exemplary embodiment” indicates that the exemplary embodiment described can include a particular feature, structure, or characteristic, but every exemplary embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same exemplary embodiment. Further, any feature, structure, or characteristic described in connection with an exemplary embodiment can be included, independently or in any combination, with features, structures, or characteristics of other exemplary embodiments whether or not explicitly described.

The foregoing Detailed Description is not meant to limiting. Rather, the scope of the disclosure is defined only in accordance with the following claims and their equivalents. It is to be appreciated that the foregoing Detailed Description, and not the following Abstract section, is intended to be used to interpret the claims. The Abstract section can set forth one or more, but not all exemplary embodiments, of the disclosure, and thus, is not intended to limit the disclosure and the following claims and their equivalents in any way.

The exemplary embodiments described within foregoing Detailed Description have been provided for illustrative purposes, and are not intended to be limiting. Other exemplary embodiments are possible, and modifications can be made to the exemplary embodiments while remaining within the spirit and scope of the disclosure. The foregoing Detailed Description has been described with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed.

Embodiments of the disclosure can be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the disclosure can also be implemented as instructions stored on a machine-readable medium, which can be read and executed by one or more processors. A machine-readable medium can include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing circuitry). For example, a machine-readable medium can include non-transitory machine-readable mediums such as read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; and others. As another example, the machine-readable medium can include transitory machine-readable medium such as electrical, optical, acoustical, or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.). Further, firmware, software, routines, instructions can be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc.

The foregoing Detailed Description fully revealed the general nature of the disclosure that others can, by applying knowledge of those skilled in relevant art(s), readily modify and/or adapt for various applications such exemplary embodiments, without undue experimentation, without departing from the spirit and scope of the disclosure. Therefore, such adaptations and modifications are intended to be within the meaning and plurality of equivalents of the exemplary embodiments based upon the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by those skilled in relevant art(s) in light of the teachings herein. 

What is claimed is:
 1. A phase locked loop (PLL), comprising: a time-to-digital converter (TDC) configured to measure a phase error difference between a phase of a first signal and a phase of a second signal; calibration circuitry configured to: estimate a resolution of the TDC, and compare the estimated resolution of the TDC to a target resolution; voltage doubler circuitry configured to: charge or discharge one or more switchable capacitors in accordance with a switching clocking signal to provide a supply voltage when the estimated resolution of the TDC is less than or equal to the target resolution, and skip one or more cycles of the switching clocking signal to decrease the supply voltage when the estimated resolution of the TDC is greater than the target resolution, wherein the TDC is further configured to receive operational power from the supply voltage; and a digital oscillator configured to provide the second signal in response to the phase error difference.
 2. The PLL of claim 1, further comprising: a digital low pass filter configured to provide a tuning signal in response to the phase error difference, wherein the digital oscillator is configured to adjust a frequency of the second signal and/or the phase of the second signal in response to the tuning signal.
 3. The PLL of claim 1, wherein the voltage doubler circuitry comprises: control logic circuitry configured to provide an oscillator circuitry control signal at a first logical level when the resolution of the TDC is less than or equal to the target resolution and at a second logical level when the resolution of the TDC is greater than the target resolution, oscillator circuitry configured to provide the switching clocking signal when the oscillator circuitry control signal is at the first logical level and to cease providing the switching clocking signal when the oscillator circuitry control signal is at the second logical level, and switchable capacitor circuitry configured to charge or discharge one or more switchable capacitors when the switching clocking signal is at the first logical level to provide the supply voltage and to discharge the one or more switchable capacitors to decrease the supply voltage when the switching clocking signal is at the second logical level.
 4. The PLL of claim 3, wherein the switching clocking signal is at the second logical level when the oscillator circuitry is configured to cease providing the switching clocking signal.
 5. The PLL of claim 4, further comprising: calibration circuity configured to provide, based upon the phase error difference, a voltage control signal indicative of a ratio between the estimated resolution of the TDC and the target resolution for the TDC.
 6. The PLL of claim 1, wherein the supply voltage is a digital input supply voltage, and wherein the voltage doubler circuitry is configured to scale an analog input supply voltage by a numerical factor to provide the digital input supply voltage.
 7. The PLL of claim 6, wherein the numerical factor is two.
 8. The PLL of claim 1, further comprising: digital dividing circuitry configured to digitally divide the second signal to provide a clocking signal, wherein the TDC is configured to measure a phase error difference between the phase of the first signal and a phase of the clocking signal.
 9. A method for compensating for process, voltage, and temperature (PVT) variations within a phase locked loop (PLL), the method comprising: measuring, by the PLL, a phase error difference between a phase of a first signal and a phase of a second signal; estimating, by the PLL, a resolution of a time-to-digital converter (TDC) with the PLL based upon the phase error difference; generating, by the PLL, a switching clocking signal when the estimated resolution of the TDC is less than or equal to a target resolution, the switching clocking signal switching between a first logical level and a second logical level; skipping, by the PLL, one or more clocking cycles of the switching clocking signal when the estimated resolution of the TDC is greater than the target resolution, the switching clocking signal being at the first logical level for a duration of the one or more clocking cycles of the switching clocking signal; discharging, by the PLL, one or more switched capacitor circuits when the switching clocking signal is at the first logical level; and charging, by the PLL, the one or more switched capacitor circuits when the switching clocking signal is at the second logical level.
 10. The method of claim 9, wherein the charging comprises: charging the one or more switched capacitor circuits from a first supply voltage when the switching clocking signal is at the second logical level.
 11. The method of claim 10, wherein the discharging comprises: discharging the one or more switched capacitor circuits when the switching clocking signal is at the second logical level to provide a second supply voltage.
 12. The method of claim 11, wherein the discharging further comprises: discharging the one or more switched capacitor circuits over the duration of the one or more clocking cycles of the switching clocking signal to decrease the second supply voltage.
 13. The method of claim 12, wherein the discharging the one or more switched capacitor circuits over the duration of the one or more clocking cycles of the switching clocking signal comprises: discharging the one or more switched capacitor circuits over the duration of the one or more clocking cycles of the switching clocking signal to decrease the second supply voltage to compensate for the PVT variations within the PLL.
 14. The method of claim 11, further comprising: providing, by the PLL, the second supply voltage to the TDC.
 15. A system for compensating for process, voltage, and temperature (PVT) variations within a phase locked loop (PLL), the system comprising: a time-to-digital converter (TDC) configured to measure a phase error difference between a phase of a first signal and a phase of a second signal; an oscillator configured to: be enabled to generate a switching clocking signal when a resolution of the TDC is less than or equal to a target resolution for the TDC, the switching clocking signal switching between a first logical level and a second logical level, and be disabled to skip one or more clocking cycles of the switching clocking signal when the resolution of the TDC is greater than the target resolution for the TDC, the switching clocking signal being at the first logical level for a duration of the one or more clocking cycles of the switching clocking signal; and one or more switchable capacitors configured to be discharged when the switching clocking signal is at the first logical level and to be charged when the switching clocking signal is at the second logical level to provide a supply voltage, wherein the TDC is further configured to receive operational power from the supply voltage.
 16. The system of claim 15, further comprising: calibration circuitry configured to estimate the resolution of the TDC based on the phase error difference.
 17. The system of claim 15, wherein the one or more switchable capacitors are configured to be charged from a second supply voltage when the switching clocking signal is at the second logical level.
 18. The system of claim 15, wherein the one or more switchable capacitors are configured to scale the second supply voltage by a numerical factor to provide the supply voltage.
 19. The system of claim 18, wherein the numerical factor is two.
 20. The system of claim 15, further comprising: a digital oscillator configured to provide the second signal in response to the phase error difference. 